The invention relates to a method and an apparatus for continuously unwinding a yarn from a feed yarn package, as well as a method and a texturing machine for texturing a synthetic multifilament yarn.
Various methods and apparatus for unwinding a yarn are known and used in textile machines, wherein a yarn is withdrawn from a feed yarn package and treated or processed. In so doing, the yarn is continuously unwound from the feed yarn package, and advanced to the subsequent process. To ensure a continuous process sequence, the trailing yarn end of the feed yarn package is knotted to the leading yarn end of a second feed yarn package, which is referred to as a reserve package in the present application. Thus, after unwinding the feed yarn package, an automatic change occurs to the reserve package, whose trailing yarn end is in turn knotted to a leading yarn end of a further package, so that the process operates continuously. However, in the subsequent treatment or processing of the yarn, the knot-type piecings constitute problem spots, which may lead to defects in the finished product. In the extreme case, the piecing may separate, so that a yarn break results.
In the texturing of a yarn, the yarn undergoes an intensive treatment during processing. In this process, a crimped yarn is produced from a flat yarn. To this end, as is known, for example from EP 0 641 877 and corresponding U.S. Pat. No. 5,644,908, the yarn is twisted and, for purposes of setting, it is heat treated in its twisted condition. In so doing, the piecing between a trailing yarn end of a feed yarn package and a leading yarn end of a second feed yarn package (reserve package) influences the twist distribution, which results in an irregular crimp. In the further processing of the crimped yarn, such defects may lead, for example, to dye imperfections.
It is therefore an object of the invention to provide a method and an apparatus of the initially described kind for continuously unwinding a yarn, which ensure that a yarn of uniform quality is supplied to a subsequent process.
A further object of the invention is to make available a method and a texturing machine for texturing a synthetic yarn, for purposes of producing from predetermined feed yarn packages with a flat yarn defined packages with crimped yarn, which can be associated to the feed yarn package.
The above and other objects and advantages of the invention are achieved by the provision of a method and apparatus wherein the yarn is serially withdrawn from the feed yarn package and the yarn reserve package so that the withdrawn yarn is transferred from the yarn feed package to the yarn reserve package. Also, a sensor is provided which senses when the withdrawn yarn is transferred from the feed yarn package to the yarn reserve package, and the sensor then generates a responsive signal.
The invention distinguishes itself in that after unwinding the complete feed yarn package, a signal is generated. This indicates, for example, to an operator that a change of the feed yarn is imminent in the treatment or processing operation. Thus, there exists a correspondence between the finished or end product and the feed yarn package. The operator is able to initiate measures for purposes of avoiding possible occurrences of defects because of the knot-type piecing in the yarn. To detect a change from the feed yarn package to the reserve package, a sensor is used which indicates the transition of yarn from the feed yarn package to the reserve package (yarn change) by emitting a signal. To this end, it is basically possible to use three different embodiments of the method according to the invention. In a first embodiment of the method, the yarn continuously advances through the sensor. To this end, the sensor is designed and constructed such that it generates a signal, when a knot-type piecing passes by, which represents the trailing yarn end of the feed yarn package and the leading yarn end of the reserve package. This embodiment of the method has the advantage that the yarn can be scanned independently of the location in any location along the machine. Likewise, it is possible to use a device of the subsequent process, which detects a process parameter, for example, a yarn tension. In this process, the discontinuity of the signal of the device is evaluated for indicating the passage of the piecing.
In a further advantageous embodiment of the method, only a partial length of the yarn, which comprises a yarn length at the trailing end of the feed yarn package and a yarn length at the leading yarn end of the reserve package, advances through the sensor. To this end, the sensor is arranged between the feed yarn package and the reserve package. Since during the unwinding of the feed yarn package, the trailing yarn end of the feed yarn package and the leading yarn end of the reserve package extend in a loop loosely between the two packages, this variant of the method provides a possibility of scanning the yarn only directly before the yarn change. This minimizes the influence of scanning on the yarn.
A particularly simple and effective development of the invention is given by the further embodiment wherein the trailing yarn end of the feed yarn package and the leading yarn end of the reserve package are stopped, while unwinding the feed yarn package. It is thereby possible to use the movement of a yarn length in the region for signaling the yarn change. This embodiment of the method is characterized in particular in that it requires simple apparatus components for carrying out the method. To this end, the yarn length may be inserted, for example, in a sensor, which generates a signal, as soon as the yarn length no longer contacts it.
At this point, it should be mentioned that the method can be carried out using a variety of designs for the sensor. Thus, for example, it is possible to use mechanical, optical, or capacitive sensors, which generate an electrical, mechanical, or pneumatic signal.
To alert an operator of the signal, it is further proposed that the signal activates a signaler for a visual or acoustic display.
In a particularly advantageous further development of the invention, the signal is supplied to a control unit of the process for purposes of preparing or initiating an intervention in the process. This embodiment of the method is of advantage in particular in the case of automatic process sequences. Thus, it can be realized that, for example, the empty feed yarn package is replaced with a new package, the leading yarn end of which is knotted to the trailing yarn end of the reserve package. With that, it is likewise possible to document the yarn change, in that, for example, the position and the time are registered and stored. These data may form the basis for a further evaluation in quality management.
In processes wherein the piecing leads to occurrences of defects, or wherein it is necessary to maintain a correspondence between the feed yarn and the finished or end product, the embodiment of the method will be especially advantageous, wherein in the event of an unanswered signal, the process will be interrupted for a period of time. For example, in a texturing process, a flat feed yarn is textured in the process and subsequently wound as a textured or crimped yarn on a package. In machines of this kind, a plurality of end packages are wound with a crimped yarn from one feed yarn package. To this end, it is necessary that a package doff be performed in the takeup. During the package doff, a suction device removes the processed yarn to waste. The invention makes it now possible to initiate in such machines a package doff in the takeup in a purposeful manner. The special advantage lies in that it is possible to remove as waste the partial length of the yarn that contains the piecing.
A further advantageous development of the invention provides that in the subsequent process a monitoring mechanism is activated, which detects certain quality parameters for maintaining a uniform quality. With that, it is possible to initiate a process change or process interruption in the case of an unacceptable variation of the quality parameter, for example, the yarn tension. It is possible to detect as quality parameters, process parameters, such as, for example, yarn speed, yarn tension, or product parameters, such as, for example, yarn temperature.
To ensure a correspondence between the yarn of the feed package and the respective product, an embodiment of the invention is especially advantageous, wherein a controller causes a change of the feed yarn package and a registration of the new feed yarn package, when a signal is received. To this end, it is possible to activate, for example, a transfer device, which selects a feed yarn package with a certain yarn and supplies it to the position vacated by the unwound feed yarn package. Thus, there exists the possibility of not only coordinating the feed yarn and end product, but also of correlating material-specific occurrences in the process back to the respective initial product. However, the new feed yarn package may also be registered by manually inputting identifications of the respective feed yarn package. Advantageously, the registration remains stored inside the controller, until the replaced feed yarn package is unwound as a result of the yarn change.
It is preferred to use the invention in processes, wherein a yarn is treated, which subsequently results in an end product in a further processing operation. This enables a method of texturing a multifilament synthetic yarn, wherein the produced package can be exactly specified as regards its starting material by reference to the feed yarn package. Thus, the method of the invention distinguishes itself in particular in that it permits producing packages with crimped yarn, which hold from the start to the end, a yarn of a uniformly high quality. Defects by knot-type piecings may be treated individually. In the case that monitoring of a quality parameter results in no unacceptable variation of the quality parameter caused by the piecing, the package will be produced without interruption. When a limit value of the quality parameter is exceeded, or in general, when a yarn change signal is waiting, winding of the crimped yarn may be interrupted, for example, by automatically doffing the package.
In the texturing of synthetic yarns, machines are used, wherein a plurality of processing stations are arranged in tiers side by side. With the use of such machines, it is possible to use in a very advantageous manner an embodiment of the method wherein each takeup device is associated to two creel positions, which accommodate the feed yarn package and the reserve package. The registrations of the feed yarn package and reserve package are linked to the respective creel positions and stored in the control system, so that based on the currently active creel position, the produced package can be exactly specified as regards the starting material.
The method of the present invention renders it possible to specify the piecing in the yarn by a winding time and a yarn length, which may be attached to the package as a data printout.
In the case where a plurality of packages are produced from one feed yarn package, it is preferred to use the embodiment wherein each package which has been wound from one feed yarn package receives an identification. When a yarn change is signaled, the identification will be changed for subsequent packages, since same are produced from a different feed yarn. With that, it is possible to trace the crimped yarn back to the spinning process in which the flat yarn was produced.
A further categorization of produced packages can be realized in that the package containing the yarn change and, thus, the piecing receives an additional identification. Such a categorization is especially advantageous to distinguish in weaving between warp yarn and weft yarn packages.
The identification may occur in a simple manner by a numbering that is restarted after each yarn change.
For carrying out the method of the present invention, an apparatus is provided which facilitates successive processing of even different yarns in one process without a major interruption. To this end, a sensor is provided that detects and signals the change of the yarn from the feed yarn package to the yarn of the reserve package.
To arrange the sensor in the apparatus for scanning the yarn, at least two different embodiments of the apparatus according to the invention are possible, which are dependent on the type of sensor. Especially preferred is the embodiment which employs a sensor that scans the yarn continuously. Also, it is possible to arrange the sensor between the feed yarn package and the reserve package. In such instance, the yarn length that is formed by the trailing end of the feed yarn package and the leading end of the reserve package and remains in a loop between the packages, is scanned in a simple manner in that the sensor detects the movement of the yarn length.
To be able to initiate corresponding measures during the yarn change, the sensor preferably connects to a signaling device.
In the case of automatically proceeding processes, the sensor is preferably connected to a controller which controls the proceeding processes.
The invention also provides for a texturing machine which provides a further solution to the underlying problem. Since in the texturing process, improvement of the yarn is possible only by a significant intervention in the structure of the yarn, it is necessary to treat separately in particular irregularities in the yarn, as are caused by a knot-type piecing. The texturing machine of the present invention makes it possible to texture and wind a yarn continuously and with a uniform quality irrespective of a change to the yarn of a reserve package, when the feed yarn package is unwound.
In this connection, it is preferred to use an embodiment of the texturing machine wherein the sensor is arranged between two creel positions, so that the connecting yarn length can be scanned. This permits a simple layout and arrangement of the sensor. Also, it is no longer necessary to scan the yarn continuously. Only in the case of the yarn change, will the yarn length which extends with the piecing between the two packages, be withdrawn. The movement of the yarn length is detected and signaled by the sensor.
Preferably, such sensors are designed and constructed as yarn detectors, wherein the yarn length is held in an inoperative position, and wherein the movement of the yarn length causes the yarn detector to move to a signaling position and generate a signal. The signaling can generated in a simple manner by means of a contact switch.
When sensors are used, which continuously scan the yarn optically or mechanically, it will be advantageous to position the sensor in the yarn path downstream of the creel and upstream of the first feed system.
Thus, it is proposed, among other things, to design and construct the sensor as a yarn tensiometer, which measures the tension on the advancing yarn and generates a signal, when a limit value of the yarn tension is exceeded. In this connection, one assumes that when the yarn changes from the feed yarn package to the reserve package, the unwinding behavior of the yarn varies for a short time and, thus, leads to a variation in the yarn tension. It is preferred to use this further development of the texturing machine in processes, wherein the actual piecing exerts no significant influence in the further processing of the crimped yarn. To that extent, a signal is generated only in the case of a deviation from a predetermined limit value of the yarn tension.
To alert an operator of a signal visually or acoustically, the sensor connects to a signaling device, which may be in form of a lamp or siren.
To be able to intervene in the process automatically, it is preferred to construct the texturing machine with the sensor connected to a controller which controls the operation of the machine.
In such machine, the controller comprises means for detecting, evaluating and outputting quality parameters and means for linking the quality parameters with signals that are dependent on the yarn change. The texturing machine of the present invention is thus suited to perform a continuous quality monitoring from the feed yarn package to the wound package, so as to make thus available a high-quality yarn for further processing.